According to the diversification of energy resources, solar power plant that makes use of sunlight has been spreading. From the beginning, a small-scale power plant set on a roof of a house has been attracting attention. However, with the lack of energy sources and suppression of emission of CO2 in recent years in the background, construction of large-scale photovoltaic power plants (so-called mega solar power plants) exceeding 1000 kW has been actively performed. In the following explanation expediently, an installation location of the photovoltaic power plant is referred to as “power plant site”, a location of the power plant site is referred to as “field”, a unit solar panel is referred to as “solar module”, several to twenty modules integrated in series and formed in a long panel shape are referred to as “solar string”, and a parallel array of a larger number of “solar strings” is referred to as “solar array” as well.
In the construction of the photovoltaic power plant (solar power plant) of this type, a plurality of solar modules are integrated by parallel beams and a module supporting frame of a frame-like body as solar strings (commonly called solar panels) and the solar strings are arrayed in an array shape on stands provided in a power plant site. In general, the assembly and setting work of the solar strings is performed in the power plant site (e.g., Patent Document 1). There is also known a method of assembling the solar strings in a factory, storing the solar strings in a container, and transporting the solar strings to the power plant site (Patent Document 2).